Manufacture of urea and of intermediate products



,UNIT D- STATES PATENT YOFFICE.

CARL BOSCH, OF LUDWIGSH AFEN-ON-THE-RHINE, GERIMIIANY, ASSIGNOR, BY MESNE ASSIGNMENTS, .TO THE CHEMICAL FOUNDATION, INC., A CORPORATION OF DELA- fication.

The value of urea as a fertilizer is being more and more fully recognized. As is well known this compound can be prepared by heating ammonium carbamate in a closed vessel, but experiments conducted with the object of manufacturing urea by this reaction proved that it is diificult or impossible tomanufacture the ammonium carbamate required according to the methods hitherto known.

According' tmthe present invention ammonium carbamate or a mixture of this v body with ammonium carbonate can readily be manufactured by bringin together am- .-monia and carbonic acid, C under pressure, such pressure amountlng preferably to three or more atmospheres. This can be done by introducing into a vessel capable of withstanding the pressure atwhich it is de-' sired to eifect the reaction ammonia and carbonic acid either in the gaseous state or one of them or both in the'liquefied form, both being introduced either simultaneously, or

better successively. The temperature rises and when means are taken to check it by suitable cooling it is not possible even in large apparatus, and when introducing gases fast, to prevent dangerous pressure I arislng. Mixtures of ammonium carbamate with ammonium carbonate or ammonium carbonate asthe soleproduct can be obtained if the reaction is performed in the presence of water, the proportion of which,

if mixtures of ammonium carbamate andammonium carbonate are to be formed monium bicarbonate, or of a mixture containing this salt..- e v If it is desired to convert the ammonium I carbamate into urea at once, the conversion can be effected in the same vessel and the WARE. 1

MANUFACTURE OF UREA AND OF INTERMEDIATE PRODUCTS.

1,344,673. Specification of Letters Patent.

' Hoilh'awing.

Patented June 29, 1920.

Application filed January 21, 1915. 'Serial No. 3,559.

heat of formation of the ammonium carbamate can be utilized for its conversion into urea.

This process renders the manufacture of urea and ammonium carbamate possible on the large scale in a small space and without loss of ammonia and carbonic acid.

The following examples serve to further illustrate the nature of the invention, but

the invention is not confined to the examples.

E sample 1.

Take an autoclave capable of withstanding great pressure, and which is lined with lead or which is silvered, and furnished with means for cooling and heating and with the necessary inlet and outlet pipes.

Pump into this gaseous ammonia or fill in liquid ammonia. Introduce while cooling sufiicient carbon dioxid for the formation of the ammonium carbamate. If it is desired to manufacture ammonium carbamate as the end product.-for which purpose the temperature should during the reaction not surpass about'lOO to 110 centigradethe Vessel is allowed to cool, whereupon the contents form a solid mass of ammonium carbamate. If it is -desired to convert the product at once into urea, the cooling is only carried so far that the pressure doesfnot substantially surpass that of the subsequent treatment to form urea, viz, about thirty to fifty atmospheres, and after the substances are mixed the temperature is maintained at about 130 to 140 degrees until no further. conversion into urea takes place.

- Example 2.

Introduce liquid ammonia into a vessel capable of withstanding pressure, and then from 10 to 20% of its weight of water, and finally pump into the vessel the quantity of carbon dioxid necessary for the conversion of ammonia into ammonium carbamate. If desired the water need not be introduced into the vessel separately but together with either of the other materials.

Example 3.

Introduce solid ammonium. bicarbonate (say seventy-nine pounds) and the requisite quantity of ammonia (seventeen pounds) into a vessel capable of withstanding pressure, and heat the mixture while stirring, to about 5 0 to 100 degrees centigrade. Am-

.monium carbamate and water are formed,

. for instance, instead of the liquid ammonia,

or a part of it, concentrated aqueous ammonia may be used. In this case, more or less ammonium carbonate is formed, besides ammonium carbamate, indeed, ammonium carbonate may be the sole product.

I claim 1. The manufacture of ammonium carbamate by bringing together ammonia and carbonic acid under pressure of three atmospheres or more.

2. The manufacture of ammonium carbamate which consists in bringing together,

under pressure of threeor more atmosphere s, ammonia and ate. v

3. The'manufacture of ammonium carbamate which consists in bringing together ammonia and carbon dioxid at a pressure of three atmospheres or more and ammonium bicarbonate.

I 4. The manufacture of urea by first preparing ammonium carbamate by bringing together ammonia and carbonic acid under ammonium bicarbonpressilre whereupon the still hot reaction mass is maintained at about 130 to 140 decAR'L oson.

Witnesses ARTHUR DENONVILLE, BOHAMES, FEHMEL. 

